In terms of vaccinations, I take my cues from the CDC and information from each of the countries we visit.
You can find the CDC information for Japan here: http://wwwnc.cdc.gov/travel/destinations/traveler/none/japan
For Thailand, here are the CDC recommendations: http://wwwnc.cdc.gov/travel/destinations/thailand/traveler/packing-list
Finally, for Bhutan here are the CDC recommendations: http://wwwnc.cdc.gov/travel/destinations/traveler/none/bhutan
Take a look at this information. You can make your own decisions about which vaccinations to take. In my case, I have Hep A, B, and Typhoid as my minimum vaccinations for these parts of the world. In addition, I use bug repellant and, specifically, Permethrin, a wash-in bug repellant: http://www.rei.com/product/768970/sawyer-permethrin-pump-spray-24-oz.
In addition to dealing with personal health questions, it’s always good to eat carefully….avoid food that is not prepared in front of you or food that has been sitting out…when eating street food, choose food stalls that prepare food in front of you….watch the process.
Finally, some foods, like unpeeled fruit and vegetables, can transmit disease via the skin of the fruit or veggie…lettuce products seem to be a serious concern because of handling methods as well as the kinds of pesticides and fertilizers used.
My advice? Be careful and be wise in food selection!